Waveguide display

ABSTRACT

An apparatus (e.g. a display) including a display substrate and a waveguide. The waveguide may guide ultraviolet light from the light source onto the display substrate. The display substrate may include light emitting material configured to emit visible light in response to absorption of the ultraviolet light.

This patent application in a continuation-in-part of pending U.S. patentapplication Ser. No. 10/843,083 (filed May 10, 2004), which claimspriority to U.S. Provisional Patent Application No. 60/470,530 (filedMay 15, 2003), both of which are hereby incorporated by reference intheir entirety. This patent application is a continuation-in-part ofpending U.S. patent application Ser. No. 11/107,203 (filed Apr. 15,2006), which claims priority to U.S. Provisional Patent Application Nos.60/563,376 (filed Apr. 19, 2004), 60/579,067 (filed Jun. 10, 2004),60/586,746 (filed Jul. 10, 2004), 60/590,469 (filed Jul. 24, 2004),60/598,527 (filed Aug. 3, 2004), 60/599,826 (filed Aug. 8, 2004),60/626,152 (filed Nov. 8, 2004), 60/645,245 (filed Jan. 20, 2005), and60/658,242 (filed Mar. 3, 2005), all of which are hereby incorporated byreference in their entirety. This patent application is acontinuation-in-part of U.S. patent application Ser. No. 11/367,285(filed Mar. 3, 2006), which claims priority to U.S. Provisional PatentApplication No. 60/658,242 (filed Mar. 3, 2005), both of which arehereby incorporated by reference in their entirety. This patentapplication is a continuation-in-part of pending U.S. patent applicationSer. No. 11/464,362 (filed Aug. 14, 2006), which is a continuation ofU.S. patent application Ser. No. 10/848,489 (filed May 18, 2004 andissued as U.S. Pat. No. 7,090,355), which claims priority to U.S.Provisional Patent Application No. 60/471,968 (filed on May 19, 2003),all of which are hereby incorporated by reference in their entirety.This patent application is a continuation-in-part of pending U.S. patentapplication Ser. No. 11/332,792 (filed Jan. 14, 2006), which is acontinuation of U.S. patent application Ser. No. 10/979,131 (filed onNov. 3, 2004 and issued as U.S. Pat. No. 6,986,581), which claimspriority to U.S. Provisional Patent Application No. 60/516,939 (filed onNov. 3, 2003), all of which are hereby incorporated by reference intheir entirety. This patent application claims priority to pending U.S.Provisional Patent Application Nos. 60/845,799 (filed Sep. 18, 2006) and60/854,504 (filed Oct. 26, 2006).

BACKGROUND

The reproduction of images has had a positive effect on many people'slives. One of the earliest technologies for reproducing images was themovie projector, which allowed for audiences to view theatricalproductions without live actors and actresses. Televisions wereinvented, which allowed people to watch moving pictures in the comfortof their own homes. The first televisions were cathode ray tube (CRT)televisions, which is a technology that is still being used today.During the computer age, it has been desirable to reproduce images whichare output from computers through monitors. Like many televisions, manycomputer monitors use CRT technology.

Other technologies have been developed as substitutes for CRTtechnology. For example, liquid crystal display (LCD) technology iscommonplace for both computer monitors and televisions. A LCD is arelatively thin display, which is convenient for many people. Otherexamples of displays are plasma displays, rear projections displays, andprojectors. As display technology has improved, many new applicationsare being developed. For example, many attempts have been made todevelop displays with relatively high contrast images. However, therehave been many technical challenges that have prevented optimization ofimage contrast. Specifically, it has been difficult to minimize theamount of white light emitted from a display, which may detract from thecontrast of the image displayed. It may also be desirable for display tobe relatively thin for both aesthetic appearances and practicalimplementation. For example, thin display (e.g. plasma display and LCDdisplay) may be mounted on walls or placed on a table with a relativelysmall width.

SUMMARY

In accordance with embodiments, an apparatus (e.g. a display) mayinclude a display substrate and a waveguide. The waveguide may guideultraviolet light from the light source onto the display substrate. Thedisplay substrate may include light emitting material configured to emitvisible light in response to absorption of the ultraviolet light.

In embodiments, since ultraviolet light is converted to visible light byabsorption at light emitting material, relatively high-contrast imagesmay be displayed. Further, a waveguide may allow for the thickness of adisplay to be relatively small, maximizing the aesthetic appearance ofthe display and/or maximizing practical implementation, in accordancewith embodiments.

In embodiments, the display substrate is a substantially dark substratethat is substantially transparent to ultraviolet light. Light emittingmaterial may be configured to emit visible light in response toabsorption of ultraviolet light. Light emitting material may include aplurality of light emitting particles, with each of the plurality oflight emitting particles having a diameter less than about 500nanometers.

DRAWINGS

FIG. 1 is an example diagram of a display with images being emitted froma substantially dark substrate, in accordance with embodiments.

FIG. 2 is an example diagram of a front projection display illuminatedwith excitation light from a light source, in accordance withembodiments.

FIG. 3 is an example diagram of a rear projection display illuminatedwith excitation light from a light source, in accordance withembodiments.

FIG. 4 is an example diagram of light emitting particles dispersed in asubstantially transparent substrate, in accordance with embodiments.

FIG. 5 is an example diagram of light emitting particles disposed on asurface of a substantially transparent substrate, in accordance withembodiments.

FIG. 6 is an example diagram of a display with an anti-reflective layer,a fluorescent layer, a reflective layer, and a light absorbing layer, inaccordance with embodiments.

FIG. 7 is an example diagram of a display with a visible lightanti-reflective layer, fluorescent layer, visible light reflectivelayer, visible light absorbing layer, and an ultraviolet lightanti-reflective layer, in accordance with embodiments.

FIGS. 8 and 9 are example diagrams of displays having waveguidesincluding two reflectors, in accordance with embodiments.

FIG. 10 is an example diagram of a display having a waveguide substrate,in accordance with embodiments.

FIGS. 11 and 12 are example diagrams of display having a waveguidesubstrate and a curved reflector, in accordance with embodiments.

FIG. 13 is an example diagram of a display having two waveguidesubstrates of different refractive indices, in accordance withembodiments.

DESCRIPTION

FIG. 1 is an example diagram of a display, in accordance withembodiments. Substrate 14 may be a substantially dark substrate. Viewer10 sees images (e.g. circle 15 and triangle 16) that are created atsubstrate 14. Substrate 14 may be part of a front projection or rearprojection display.

FIGS. 2 and 3 are example diagrams of transparent displays illuminatedwith excitation light (e.g. ultraviolet light or infrared light) from alight source 18 (e.g. projector, LED array, laser, or other light sourcethat emits ultraviolet or infrared light), in accordance withembodiments. Substrate 14 may receive excitation light from a lightsource 18. The received excitation light may be absorbed by lightemitting material at substrate 14. When the light emitting materialreceives the excitation light, the light emitting material may emitvisible light. Accordingly, images (e.g. circle 15 and triangle 16) maybe created at substrate 14 by selectively illuminating substrate 14 withexcitation light.

The excitation light may be ultraviolet light, in accordance withembodiments of the present invention. If the excitation light isultraviolet light, then when the light emitting material emits visiblelight in response to the ultraviolet light, a down-conversion physicalphenomenon occurs. Specifically, ultraviolet light has a shorterwavelength and higher energy than visible light. Accordingly, when thelight emitting material absorbs the ultraviolet light and emits lowerenergy visible light, the ultraviolet light is down-converted to visiblelight because the ultraviolet light's energy level goes down when it isconverted into visible light. In embodiments, the light emittingmaterial is fluorescent material.

The excitation light may be infrared light, in accordance withembodiments of the present invention. If the excitation light isinfrared light, then when the light emitting material emits visiblelight in response to the infrared light, an up-conversion physicalphenomenon occurs. Specifically, infrared light has a longer wavelengthand lower energy than visible light. Accordingly, when the lightemitting material absorbs the infrared light and emits higher energyvisible light, the infrared light is up-converted to visible lightbecause the infrared light's energy level goes up when it is convertedinto visible light. In embodiments, the light emitting material isfluorescent material. In the up-conversion physical phenomenon,absorption of more than one infrared light photon may be necessary forthe emission of every visible light photon.

In embodiments illustrated in FIG. 2, excitation light is output bylight source 18, with the light source projecting light from the viewerside of the substrate 14. Accordingly, the substantially dark substrate14 may be implemented in a front projection display. In embodimentsillustrated in FIG. 3, excitation light is output be light source 18,with the light source projecting light from the opposite side ofsubstrate 14 than the viewer 10. One of ordinary skill in the art willappreciate that projection could include any transmission of light intothe substrate 14, whether the light source 18 is independent ofsubstrate 14 or integrated into substrate 14.

Light source 18 may be a digital projector. In embodiments, light source18 is a micro-mirror array (MMA) projector (e.g. a digital lightprocessing (DLP) projector). A MMA projector that outputs ultravioletlight may be similar to a MMA projector that outputs visible light,except that the color wheel has light filters that are tailored to theultraviolet light spectrum. In other embodiments, the light source 18 isa liquid crystal display (LCD) projector. In embodiments, the lightsource 18 may be a liquid crystal on silicon (LCOS) projector. Inembodiments, the light source 18 may be an analog projector (e.g. aslide film projector or a movie film projector). In embodiments, lightsource 18 may be a laser. In down-conversion embodiments, the outputfrom light source 18 may be ultraviolet light. In up-conversionembodiments, the output from light source 18 may be infrared light. Oneof ordinary skill in the art would appreciate other types of projectors,lasers or other light radiating devices which may be used to projectultraviolet light on substrate 14.

FIG. 4 is an example diagram of light emitting material (e.g. lightemitting particles 21) dispersed in a substantially dark substrate,according to embodiments. When excitation light is absorbed by the lightemitting particles 21, the light emitting particles emit visible light.Accordingly, in down-conversion embodiments, when ultraviolet light isabsorbed by light emitting particles 21, visible light is emitted fromthe light emitting particles. Likewise, in up-conversion embodiments,when infrared light is absorbed by light emitting particles 21, visiblelight is emitted from the light emitting particles. FIG. 5 is an examplediagram of light emitting particles 25 disposed on a surface ofsubstrate 14. Light emitting particles 25 may be integrated intosubstrate 14 by being coated on substrate 14. In embodiments substrate14 is a substantially homogeneous substrate with light emittingparticles (e.g. particles 21 or particles 25) integrated into thesubstrate 14. Although substrate 14 may be substantially homogeneous,one of ordinary skill in the art will appreciate that the concentrationof light emitting particles integrated into substrate 14 may be varying(e.g. concentration of particles on or near the surface of substrate14).

Light emitting material (e.g. light emitting particles 21 and lightemitting particles 25) may be fluorescent material, which emits visiblelight in response to absorption of electromagnetic radiation (e.g.visible light, ultraviolet light, or infrared light) that is a differentwavelength than the emitted visible light. The size of the particles maybe smaller than the wavelength of visible light, which may reduce oreliminate visible light scattering by the particles. Examples ofparticles that are smaller than the wavelength of visible light arenanoparticles or molecules. According to embodiments, each of the lightemitting particles has a diameter that is less than about 500nanometers. According to embodiments, each of the light emittingparticles has a diameter that is less than about 400 nanometer.According to embodiments, each of the light emitting particles has adiameter that is less than about 300 nanometer. According toembodiments, each of the light emitting particles has a diameter that isless than about 200 nanometers. According to embodiments, each of thelight emitting particles has a diameter that is less than about 100nanometers. The light emitting particles may be individual molecules.

Different types of light emitting particles (e.g. light emittingparticles 21 and light emitting particles 25) may be used together thathave different physical characteristics. For example, in order to emitcolor images in substrate 14, different types of light emittingparticles may be utilized that are associated with different colors. Forexample, a first type of light emitting particles may be associated withthe color red, a second type of light emitting particles may beassociated with the color green, and a third type of light emittingparticles may be associated with the color blue. Although the examplefirst type, second type, and third type of light emitting particles areprimary colors, one of ordinary skill in the art would appreciate othercombinations of colors (e.g. types of colors and number of colors) inorder to facilitate a color display.

In down-conversion embodiments, light emitting particles which emit redlight may include Europium, light emitting particles which emit greenlight may include Terbium, and light emitting particles which emit blueor yellow light may include Cerium (and/or Thulium). In up-conversionembodiments, light emitting particles which emit red light may includePraseodymium, light emitting particles which emit green light mayinclude Erbium, and light emitting particles which emit blue light mayinclude Thulium. In embodiments, light emitting particles arefluorescent molecules that emit different colors (e.g. red, green, andblue). In embodiments, light emitting particles are included in pureorganic or organo-metallic dyes.

Different types of light emitting particles may absorb different rangesof excitation light to emit the different colors. Accordingly, thewavelength range of the excitation light may be modulated in order tocontrol the visible color emitted from the light emitting particles insubstrate 14. In embodiments, different types of light emittingparticles may be mixed together and integrated into substrate 14. Bymodulating the wavelength of the excitation light, along with spatialmodulation and intensity modulation of the excitation light, visiblelight with specific color characteristics can be created in substrate14. For example, by selectively exciting specific combinations ofdifferent types of light emitting particles associated with primarycolors, virtually any visible color can be emitted from substrate 14.

In embodiments, median particle size of fluorescent materials may not belimited to particles having a diameter less than approximately 500 nm.For example, in embodiments, a substantially transparent fluorescentdisplay screen may include fluorescent materials that have similaroptical properties as the host (e.g. a host substantially transparentsubstrate. In embodiments, fluorescent materials may have a refractiveindex than is substantially the same or relatively close to therefractive index of the host. In embodiments, where fluorescentmaterials are refractive index match to the host, the particle size ofthe fluorescent materials could be larger than 500 nm. However, theparticle sizes may also be less than 500 nm, in accordance withembodiments. In embodiments, a transparent screen with refractiveindexed matched fluorescent materials may be implemented with a varietyof backgrounds (e.g. a substantially dark substrate), withoutsignificantly altering the substrate appearance. In embodiments,refractive index matched fluorescent materials may be implemented with adark filter that transmit UV light (e.g. in a rear-projection display).

In DLP projector embodiments, the wavelength of ultraviolet lightemitted from a DLP projector can be modulated using a color wheel withspecific ultraviolet pass filters. Similar modulation techniques may beutilized in other projector embodiments and laser embodiments. Inembodiments, multiple projectors and multiple lasers may be utilized,each being associated with a specific ultraviolet wavelength range toexcite a specific type of light emitting particle, to output a specificcolor of light.

FIG. 6 is an example diagram of a display with anti-reflective layer 22,fluorescent layer 24, reflective layer 26, and light absorbing layer 28,in accordance with embodiments. The substantially dark substrate 14depicted in FIG. 6 may be used in a front projection display. Lightabsorbing layer 28 may allow for high contrast images by minimizingwhite light emission. Reflective layer 26 may compensate for differentvisible color emissions based on different material properties.Fluorescent layer 24 may provide for visible light emission in responseto absorption of ultraviolet light. Anti-reflective layer 22 may reduceglare on a display and provide for higher efficiency of visible lightemission. In embodiments, the substantially dark substrate 14illustrated in FIG. 6 may be utilized in a front projection display.However, one of ordinary skill in the art would appreciate that thesubstantially dark substrate 14 illustrated in FIG. 6 may also beutilized in a rear projection display.

In embodiments, the substantially dark substrate 14 may includeanti-reflective layer 22. Anti-reflective layer 22 may be a broadband(e.g. visible and ultraviolet light) anti-reflective layer, a visiblelight reflective layer, or an ultra-violet light anti-reflective layer.In front projection display embodiments, anti-reflective layer 22 (e.g.broadband anti-reflective layer or visible light anti-reflective layer)may be used to reduce glare on a display seen by viewer 10. Reducedglare will allow for images to be displayed more clearly onsubstantially dark substrate 14. In front projection displayembodiments, anti-reflective layer 22 (e.g. broadband anti-reflectivelayer or ultraviolet light anti-reflective layer) may be used tomaximize the absorption of ultraviolet light by the light emittingmaterials (e.g. in fluorescent layer 24). In other words,anti-reflective layer 22 will reduce the amount of ultraviolet lightthat is reflected off of substantially dark substrate 14, whichincreases the amount of ultraviolet light that is transmitted intofluorescent layer 24 (which includes light emitting material).

In embodiments, fluorescent layer 24 includes light emitting material.The light emitting material may emit visible light in response toabsorption of excitation light (e.g. ultraviolet light).

In embodiments, reflective layer 26 may reflect light. In embodiments,reflective layer 26 is a selective waveband reflective layer. Aselective waveband reflective layer may compensate for varying emissionefficiencies of different light emitting materials. For example, iflight emitting materials that emit red light emit light at a higherintensity than light emitting materials that emit blue light, aselective waveband reflective layer may compensate for these differencesin emission efficiencies. For example, reflective layer 26 may reflectblue light with a higher intensity than reflective layer 26 reflects redlight. Likewise, reflective layer 26 may reflect the wavelengths ofultraviolet light that cause emission of blue light with a higherintensity than reflective layer 26 reflects red light.

In embodiments, light absorbing layer 28 may absorb light to maximizethe contrast of an image (e.g. circle 15 and triangle 16) seen by aviewer 10. By absorbing visible light, less white light is emitted fromthe substantially dark substrate, thus maximizing contrast. Inembodiments, light absorbing layer 28 may be transparent to ultravioletlight, but substantially absorbs visible light. In embodiments, lightabsorbing layer 28 absorbs both visible light and ultraviolet light.

FIG. 7 is an example diagram of a display with visible lightanti-reflective layer 30, ultraviolet light reflective layer 32,fluorescent layer 34, visible light reflective layer 38, visible lightabsorbing layer 40, and ultraviolet light anti-reflective layer 42.Visible light anti-reflective layer 30 may allow for higher contrastimages viewed by view 10, by reducing glare of external visible light.Ultraviolet anti-reflective layer 32 may increase the efficiency ofvisible light emitted from fluorescent layer 34. Ultravioletanti-reflective layer 32 may compensate for different emissioncharacteristics of different light emitting materials in fluorescentlayer 34, as a selective ultraviolet light reflector. Visible lightreflector layer 38 may compensate for different emission characters ofdifferent light emitting materials in fluorescent layer 34, as aselective visible light reflector. Light absorbing layer 40 may allowfor high contrast images by minimizing white light emission.Anti-reflective layer 22 may provide for higher efficiency of visiblelight emission. In embodiments, the substantially dark substrate 14illustrated in FIG. 7 may be utilized in a rear projection display.However, one of ordinary skill in the art would appreciate that thesubstantially dark substrate 14 illustrated in FIG. 7 may also beutilized in a front projection display.

One of ordinary skill in the art would appreciate that the layersillustrated in FIGS. 6 and 7 may be used in different combination,including non-inclusion of layers, without departing from the spirit ofembodiments. Further, it would be appreciated by one of ordinary skillin the art that any of the layers may further include additional layers.Other layers and/or substrates may be used in conjunction with theillustrated layers without departing from the scope of embodiments.

Example FIGS. 8 through 13 illustrate example displays including awaveguide and light emitting material, in accordance with embodiments.In embodiments, a waveguide may be implemented to guide light (e.g.ultraviolet light) from a light source to a display substrate. Thedisplay substrate may include light emitting material that emits visiblelight in response to absorption of excitation light (e.g. ultravioletlight). In embodiments, a waveguide may minimize the distance between alight source and a display substrate. For example, a 20 inch display mayuse a waveguide that is less than 1 inch thick, in accordance withembodiments. However, one of ordinary skill in the art would appreciateother dimensions of display and waveguide, in accordance withembodiments.

Example FIG. 8 illustrates a display with a waveguide including firstreflector 54 and second reflector 52, in accordance with embodiments.Excitation light from light source 50 may be projected onto firstreflector 52. The excitation light may be reflected off of firstreflector 52 and directed onto second reflector 54. The excitation lightprojected onto second reflector 54 may be reflected off of reflector 54and onto display substrate 56. Excitation light from light source 50 maybe modulated by a modulator between light source 50 and reflector 54 orby a modulator internal to light source 50, in accordance withembodiments. A modulator may modulate the excitation light based onvideo and/or picture content to be displayed on display substrate 56.

In accordance with embodiments, display substrate 56 may include lightemitting material that emits visible light in response to absorption ofexcitation light (e.g. ultraviolet light). As illustrated in exampleFIG. 8, display substrate 56 may include a substantially transparentfluorescent screen 60 and/or a ultraviolet transparent substantiallydark substrate 58. Excitation light (e.g. ultraviolet light) reflectedoff of reflector 52 may pass through substantially dark substrate 58 andinto substantially transparent fluorescent screen 60. Light emittingmaterial integrated into transparent fluorescent screen 60 may absorbthe excitation light and emit corresponding visible light to display animage, in accordance with embodiments. Substantially dark substrate 48may absorb visible light directed back into the display, which maymaximize the contrast of the image displayed on display substrate 56.

In embodiments, internal and/or external surfaces of display substrate56 may be coated with at least one anti-reflective layer (e.g. film,coating, and/or surface treatment), which may maximize opticalefficiency and/or image uniformity. In embodiments, internal and/orexternal surfaces of display substrate 56 may be treated (e.g. film,coating, or surface treatment) to minimize glare and/or maximize imagecontrast. Substantially dark substrate 58 and transparent fluorescentscreen 60 are shown for illustrative purposes, but other implementationsof display substrate 56 may be implemented, in accordance withembodiments.

In embodiments, first reflector 54 and second reflector 52 are foldingmirrors. Folding mirrors may be relatively highly reflective mirror withrelatively high reflection efficiency. In accordance with embodiments, awaveguide may include two reflectors. In embodiments, a waveguide mayinclude more than two reflectors. As illustrated in example FIG. 8,first reflector 54 and second reflector 52 may be arranged substantiallyparallel to each other, in accordance with embodiments. In embodiments,first reflector 54 and second reflector 52 may be arranged at an anglewith each other. Accordingly, projected excitation light may go throughmultiple reflections before being absorbed by light emitting material.

In embodiments, light source 50 may include a micro-mirror device. Anexample of a micro-mirror device is a Digital Light Processing (DLP)device. In embodiments, light source 50 may be a laser device includinga modulator. An example of a laser device is a laser device thatincludes a raster display engine (e.g. a 2-axis single mirror scanner ora dual-mirror scanner). Embodiments include all light sources and/ormodulators that project excitation light.

Example FIG. 9 illustrates a display with a waveguide that is relativelythin, in accordance with embodiments. As illustrated in example FIG. 9,a display includes a light source 50, first reflector 62, secondreflector 64, and display substrate 66, in accordance with embodiments.Compared with embodiments illustrated in example FIG. 8, first reflector62 and second reflector 65 may be arranged relatively close to eachother, in accordance with embodiments. Accordingly, the closer thatfirst reflector 62 and second reflector 65 are together, the thinner adisplay may be. In embodiments illustrated in example FIG. 9, lightprojected by light source 50 may have a relatively high incident angle,which may improve optical efficiency at the reflectors. In embodiments,first reflector and second reflector may be arranged at an angle. One ofordinary skill in the art will appreciate other arrangements of firstreflector and second reflector 65, without departing from the spirit andscope of embodiments.

Example FIG. 10 illustrates a display having a waveguide substrate, inaccordance with embodiments. A display may include waveguide 68.Excitation light from light source 50 may be projected into waveguide68. Excitation light projected into waveguide 68 may be internallyreflected to be projected onto display substrate 70. Internal reflectioninside waveguide 68 may include multiple internal reflections (e.g. thefour internal reflections illustrated in example FIG. 10). Any number ofinternal reflection configurations may be implemented, in accordancewith embodiments.

In embodiments, waveguide 68 may have a wedge shape. A wedge shape mayallow excitation light to be selectively internally reflected ortransmitted out of waveguide 68 and into display substrate 70. In otherwords, there may be increasingly higher incident angles of theexcitation light, such that the internal reflections will allow light tobe reflected and will allow the light to be finally transmitted intodisplay substrate 70, in accordance with embodiments. In embodiments,waveguide 68 may include solid glass, plastic slab, or other similarmaterial. The material of waveguide 68 may be substantially transparentto the excitation light (e.g. substantially transparent to ultravioletlight) from light source 50.

Example FIG. 11 illustrates a display with a waveguide that is planer,in accordance with embodiments. Waveguide 72 may have surfaces that aresubstantially parallel, in accordance with embodiments. Displaysubstrate 74 may abut waveguide 72, allowing for light to be transmittedout of waveguide 72 and into display substrate 74 based on thedifference between the refractive index of display substrate 74 andwaveguide 72. As illustrated in example FIG. 11, a curved reflector 76may be included in waveguide 72 to distribute light incident on displaysubstrate 74 and minimize the length of waveguide 72, in accordance withembodiments. Curved reflector 76 may be configured to compensate forimage distortion.

Example FIG. 12 illustrates a wedge shaped waveguide that includes acurved reflector, in accordance with embodiments. Waveguide 78 may havea wedge shape. Curved reflector 80 may be included in waveguide 78.

Example FIG. 13 illustrates a waveguide that has both a planer portionand a wedge shaped portion, in accordance with embodiments. Asillustrated in example FIG. 13, a bottom portion of first waveguide 84is planer and a top portion of first waveguide 84 has a wedge shape, inaccordance with embodiments. A display may include a second waveguide86, in accordance with embodiments. Second waveguide 86 may abut firstwaveguide 84, in accordance with embodiments. Second waveguide 86 mayhave a refractive index different (e.g. greater) than the refractiveindex of first waveguide 84, in accordance with embodiments. Lightsource 50 may project light into second waveguide 86. Light projectedinto second waveguide 86 may be transmitted into first waveguide 84 andbent at the interface of second waveguide 86 and first waveguide 84.

In embodiments, since visible light may be emitted substantiallyisotropically from light emitting material, in response to absorption ofexcitation light (e.g. ultraviolet light), the angle that the excitationis projected onto a display substrate may be substantially independentof the direction that visible light is emitted from the displaysubstrate. In other words, even though excitation light (ultravioletlight) may be transmitted into a display substrate at an angle, afterthe excitation light is absorbed by the light emitting material, theemission light (e.g. visible light) illuminates isotropically in alldirections from the display substrate, substantially unaffected and/orindependent from the incident angle of the excitation light into thedisplay substrate, in accordance with embodiments.

In embodiments, a planar waveguide (e.g. wedge shaped of rectangularshaped) may be implemented to minimize physical dimensions (e.g.thickness) of a display system. In embodiments, a waveguide may includetwo parallel mirrors, a optical plate with uniform thickness, an opticalplate having a wedge shape, and/or a hybrid of different waveguide typesto internally reflect excitation light.

The foregoing embodiments (e.g. light emitting material integration anddisplay mechanism) and advantages are merely examples and are not to beconstrued as limiting the appended claims. The above teachings can beapplied to other apparatuses and methods, as would be appreciated by oneof ordinary skill in the art. Many alternatives, modifications, andvariations will be apparent to those skilled in the art.

1. An apparatus comprising: a light source configured to projectultraviolet light; a display substrate comprising light emittingmaterial configured to emit visible light in response to absorption ofthe ultraviolet light; a waveguide configured to guide the ultravioletlight onto the display substrate.
 2. The apparatus of claim 1, wherein:the light emitting material comprises a plurality of light emittingparticles; and each of the plurality of light emitting particles has adiameter less than about 500 nanometers.
 3. The apparatus of claim 2,wherein each of the plurality of light emitting particles has a diameterless than about 400 nanometers.
 4. The apparatus of claim 3, whereineach of the plurality of light emitting particles has a diameter lessthan about 100 nanometers.
 5. The apparatus of claim 1, wherein theapparatus is comprised in a rear projection display.
 6. The apparatus ofclaim 1, comprising a light modulator configured to modulate theultraviolet light.
 7. The apparatus of claim 6, wherein the lightmodulator is a micro-mirror light modulator.
 8. The apparatus of claim1, wherein the light course is a laser beam scanner.
 9. The apparatus ofclaim 1, wherein the display substrate is a substantially dark substratethat is substantially transparent to ultraviolet light.
 10. Theapparatus of claim 1, wherein the waveguide comprises at least tworeflectors.
 11. The apparatus of claim 1, wherein the waveguidecomprises a reflector with a curved shape.
 12. The apparatus of claim 1,wherein the waveguide comprises at least one waveguide substrateconfigured to internally reflect the ultraviolet light onto the displaysubstrate.
 13. The apparatus of claim 12, wherein said at least onewaveguide substrate has a wedge shape.
 14. The apparatus of claim 12,wherein said at least one waveguide substrate comprises a firstwaveguide substrate and a second waveguide substrate.
 15. The apparatusof claim 14, wherein the first waveguide substrate and the secondwaveguide substrate have different refractive indexes.
 16. The apparatusof claim 15, wherein: the light source is configured to project theultraviolet light into the first waveguide substrate; the ultravioletlight is transmitted from the first waveguide substrate to the secondwaveguide substrate; the ultraviolet light is bent at an angle at theinterface of the first waveguide substrate and the second waveguidesubstrate; the ultraviolet light is internally reflected in the secondwaveguide substrate onto the display substrate.
 17. The apparatus ofclaim 16, wherein the first waveguide substrate has a refractive indexgreater than the second waveguide substrate.
 18. The apparatus of claim1, wherein the light emitting material is fluorescent material.
 19. Theapparatus of claim 1, wherein the light emitting material comprises: afirst material configured to emit a first visible color in response toabsorption of a first bandwidth of ultraviolet light; and a secondmaterial configured to emit a second visible color in response toabsorption of a second bandwidth of ultraviolet light, wherein thesecond visible color is different from the first visible color.
 20. Theapparatus of claim 1, wherein the waveguide comprises both a reflectorand a waveguide substrate.